1. Field of the Invention
This invention relates to a process for the preparation of alkylene glycols from the corresponding alkylene oxide in the presence of water and a catalyst. A specific example of the process is in the preparation of ethylene glycol from ethylene oxide.
2. Description of the Prior Art
The production of alkylene glycols from alkylene oxides is known and is practiced commercially. Of particular interest is the production of ethylene glycol from ethylene oxide. The thermal hydration of ethylene oxide in water produces monoethylene glycol (MEG), a major active component in antifreeze. MEG can also be used as a base material in the production of polyester fibers, resins, films and bottles.
Hydration of ethylene oxide can be through catalytic and non-catalytic means. Non-catalytic hydration of ethylene oxide to MEG requires a large excess of water to inhibit the formation of diethylene glycol (DEG) and other higher glycols. Even with a large excess of water the molar selectivity to MEG is only about 90%. In addition, the water must be distilled from the glycol to obtain a high purity product.
Catalytic hydration of ethylene oxide may use smaller amounts of water and is carried out at lower temperatures. There are numerous examples of catalysts for hydration of an alkylene oxide to alkylene glycol.
U.S. Pat. No. 4,551,566 discloses a process for the production of alkylene glycols by the hydration of alkylene oxides in the presence of a water soluble vanadate salt in a liquid medium having a pH between 5 and 12. The adjustment of the pH to this range by addition of acids or bases affects rate and selectivity of the reaction.
U.S. Pat. No. 6,316,571 discloses preparation of alkylene glycols by reacting alkylene oxide with water in the presence of a polycarboxylic acid derivative, such as salts of malonic acid, succinic acid, tartaric acid, maleic acid, adipic acid, terephthalic acid, citric acid, trimetallitic acid and pyromellitic acid, immobilized on a resin support.
U.S. Pat. No. 4,760,200 discloses a process for liquid phase hydration of alkylene oxides to the corresponding alkylene glycols in a medium containing a water miscible alkylene glycol ether cosolvent. The process may or may not use a catalyst but if a catalyst is used it may be a metallate anion, such as a vanadate or tungstate anion, in association with electropositive complexing moieties, such as tertiary amines, on a solid substrate.
U.S. Pat. No. 6,147,265 discloses a process for producing alkylene glycol from alkylene oxide with a catalyst of an anion-exchange resin with a substrate of a vinyl aromatic compound polymer and a quaternary ammonium group, such as tertiary amine, bonded to aromatic groups of the polymer via a connecting group of a chain length of three or more atoms.
U.S. Pat. No. 5,488,184 discloses a process for preparation of alkylene glycols from alkylene oxides and water in the presence of a catalyst of a solid material having electropositive sites, such as anionic exchange resins containing tertiary amines, coordinated with non-metalate and non-halogen anions. The tertiary amines may be linked to the matrix of the solid material by a benzyl group. When a quarternary ammonium type of anionic exchange resin with a bicarbonate anion, the presence of carbon dioxide is detrimental to the performance of the catalyst.
U.S. Pat. No. 3,629,343 discloses a process for the production of alkylene glycols by catalytic hydration of alkylene oxides in the presence of carbon dioxide and an ammonium halide catalyst which may be formed in situ, e.g., triethylamine and ethyl iodide to form tetraethylammonium iodide.
U.S. Pat. No. 4,937,393 discloses a method for preparing ethylene glycol or propylene glycol with a catalyst of a carboxylic acid and a carboxylic acid salt which may be a salt of a basic-nitrogen containing compound, such as an aliphatic primary secondary or tertiary amine or a cycloaliphatic primary, secondary or tertiary amine. It is preferable that the hydration reaction proceeds in the absence of carbon dioxide.
U.S. Pat. No. 4,393,254 discloses a process for the production of alkylene glycols by catalytic hydration of alkylene oxides in the presence of a heterogeneous, partially amine-neutralized sulfonic acid catalyst which are sulfonic acid-type ion exchange resins, such as a styrene-divinylbenzene copolymer matrix with pendant sulfonic acid groups, modified by passing amine through the resin to partially neutralize the sulfonic acid groups. Primary, secondary or tertiary amines may be used but tertiary amines are preferred.
U.S. Pat. No. 4,307,256 discloses a process for the preparation of alkylene glycols from the corresponding alkylene oxides in the presence of water, carbon dioxide and an organic base, such as a tertiary amine, specifically triethylamine, dimethylaniline and pyridine.